1. Field of the Invention
The present invention relates to a vehicle-mounted navigation device. More particularly, the present invention relates to a vehicle-mounted navigation device, which performs indication of a route by a map or by an arrow indicating the direction of travel of an automobile.
2. Description of Related Art
FIG. 1 is a block diagram showing a construction of a conventional vehicle-mounted navigation device. In the figure, reference numeral 1 denotes a GPS receiver. The GPS receiver 1 demodulates data from electronic waves received by an antenna 2 mounted on the vehicle and calculates a present position of the vehicle by processing such data. 3 is a CPU which inputs vehicle positional data from the GPS receiver 1 and applies corrections to the vehicle positional data based on the output of a gyroscope and a vehicle speed sensor (not shown). 4 is a CD-ROM in which secondary information data such as map data, distance between expressway interchanges and expressway tolls are recorded in a fixed format. 5 is an input device which operates the navigation device on the basis of the key input of a user. 6 is a display device which displays vehicle positional information and map information received from the CPU 3.
The operation of the conventional vehicle-mounted navigation device will be explained below.
FIG. 2 is a flowchart showing the operation of the conventional vehicle-mounted navigation device. When the vehicle-mounted navigation device is started by a key operation from the input device 5, the CPU 3 initializes the system and uptakes data with respect to the present position of the vehicle from the GPS receiver 1. Then, map data containing the present position of the vehicle is read out from the CD-ROM 4 and is displayed on the display 6 together with the vehicle present position (step ST1). A route from a present position to a destination is searched on the basis of the data to the destination input by the input device 5. The searched route is then displayed on the map.
Arrow data indicating a direction of travel may be stored in the CD-ROM 4 instead of map data and only an arrow indicating the direction of travel by the vehicle in its present position may be displayed based on the searched route.
Since the conventional vehicle-mounted navigation device is constructed as above, it is difficult to read the display contents quickly if the display screen is not large when a vehicle position is always displayed on a map. As a result, it is necessary to increase the screen size of the display device which increases the size of the device and its cost. Furthermore, in a case where the direction of travel is indicated by an arrow, display contents can be read out quickly. However, the problem has arisen that it is not possible to have detailed information in the periphery of the guided route.
The present invention is proposed to solve the above problems and has the object of providing a vehicle-mounted navigation device which can provide detailed information regarding the proximity of the destination and the proximity of the guided route to a user by simply guiding the direction of travel only by an arrow under normal condition and by shifting to indication by a map instead of the arrow under specific conditions such as when running off-route or when setting a destination, thereby to improve an ability of providing information.
A vehicle-mounted navigation device according to the present invention comprises a memory means for storing map data, a position measurement means for measuring a present position of a vehicle, a calculation means for calculating a guided route from a present position to a destination and for selecting display of the guided route on the map read out from the memory means or display of an arrow showing a direction of travel of the vehicle, and an image display means for displaying the selected display contents.
By such an arrangement, it is possible to simply guide the direction of travel only by an arrow when the vehicle is running and thus reduce the burden of the driver. Furthermore, since the display contents may be understood accurately even if the display screen is small, a small sized screen may be used which reduces the size of the display device and reduces the cost thereof.
According to the present invention, the image display means may be adapted to display an arrow indicating the direction of travel of the vehicle under normal condition and perform map display when the vehicle is running off the guided route.
In such a way, detailed information regarding the proximity of the guided route can be provided to a user, thereby to improve an ability of providing information which is needed to understand a present position accurately.
According to the present invention, the image display means may be adapted to display an arrow indicating the direction of travel of the vehicle under normal condition and perform map display when setting a destination.
In this way, detailed information from a present position to a destination is provided to a user, as a result, it is possible to improve an ability of providing information which is needed to accurately set a guided route to the destination.
According to the present invention, the image display means may be adapted to display an arrow indicating the direction of travel of the vehicle under normal condition and perform map display when the vehicle is in the environs of the destination.
In this way, detailed information regarding the environs of the destination is provided to a user and it is possible to improve an ability of providing information which is needed to accurately understand the destination.
According to the present invention, the image display means may be adapted to display an arrow indicating the direction of travel of the vehicle under normal condition and perform map display for a predetermined period of time in response to an input operation by a user.
In this way, the present position and detailed information along the guided route can be obtained according to the preference of the user.